Catalyst for the hydrogenation of unsaturated hydrocarbons and process for its preparation

ABSTRACT

The present invention relates to a catalyst for the hydrogenation of unsaturated hydrocarbons, in particular aromatics with a broad molecular weight range, a process for the production thereof and a process for hydrogenating unsaturated hydrocarbons.

The present application claims priority from European Patent Application07118871.8 filed 19 Oct. 2007.

The present invention relates to a catalyst for the hydrogenation ofunsaturated hydrocarbons, in particular aromatics with a broad molecularweight range, a process for the production thereof and a process forhydrogenating unsaturated hydrocarbons.

The catalytic hydrogenation of aromatics is well known. EP 0 290 100discloses shaped nickel-theta Al₂O₃ catalysts containing 5 to 40weight-% nickel for the hydrogenation of aromatics-containinghydrocarbons. The catalyst support used has practically no pores smallerthan 2.0 nm. The mean pore radius of the catalysts lies in the range 7.4to 10.3 nm. The nickel impregnation is effected from ammoniacalsolution.

In EP 0 398 446, a catalyst system for the hydrogenation of aromatics insolvents and white oil with high resistance to sulphur compounds isdisclosed. The catalysts contain separately on a support a hydrogenationcomponent and a metal oxide. As metals, Cu, Ni, Pt, Pd, Rh, Ru, Co ormixtures of these metals and as a metal oxide component the oxides ofAg, La, Sb, V, Ni, Bi, Cd, Pb, Sn, V, Ca, Sr, Ba, Co, Cu, W, Zn, Mo, Mn,Fe or mixtures of these oxides are disclosed. The catalyst support canconsist of Al₂O₃, SiO₂, Al₂O₃.SiO₂, TiO₂, ZrO₂ and MgO.

Still greater sulphur resistance is attained according to EP 0 974 637through a combination of a noble metal-containing supported catalyst, ametal oxide-containing and a Ni—SiO₂ catalyst. Thus, for example, aPt/Pd supported catalyst is provided at the reactor head, and beneaththis is a mixture of ZnO extrudates and Ni—SiO₂ extrudates.

JP 3076706 describes the hydrogenation of unsaturated polymers with a Pdsupported catalyst, wherein SiO₂ supports with a pore diameter of 20 to50 nm are used. In this process, however, the catalyst consumption isvery high.

U.S. Pat. No. 5,028,665 discloses a metal supported catalyst for thehydrogenation of unsaturated polymers the support thereof predominantlyhas pores of pore diameters >45 nm. The catalysts hydrogenate 90 to 100%of the olefinic compounds, but only <25% of the aromatics. Pd, Pt and Rhare described as hydrogenation-active metals.

In U.S. Pat. No. 5,612,422, a metal-SiO₂ supported catalyst is describedfor the hydrogenation of polymers with mean molecular weights of 100000, the support thereof has a pore volume which is to at least 98%constituted of pores with pore diameters >60 nm. Pt and Rh are mentionedas preferred hydrogenation-active metals.

For the hydrogenation of resins, a catalyst is disclosed in WO 01/36093A1 which contains 45 to 85% Ni on SiO₂ (14 to 45 weight-%), Al₂O₃ (1 to15 weight-%) and 0.25 to 4 weight-% Fe and has a pore volume of at least0.35 ml/g in the pore diameter range from 2 to 60 nm.

In EP 1 262 234, catalysts for the hydrogenation of aromatics with a lowtendency to cracking are described, which contain 0.1 to 2.0 weight-% ofa noble metal of the 8^(th) subgroup on a SiO₂—MgO support with a MgOcontent of 25 to 50 weight-%. The pore volume with pore diameters >4.0nm should lie in the range from 0.3 to 0.6 ml/g and that with porediameters from 0.7 to 2 nm at 0.2 to 0.3 ml/g. The pore volume with poreradii of at least 200 nm should not be greater than 0.05 ml/g.

U.S. Pat. No. 6,376,622 discloses metal-SiO₂ supported catalysts for thehydrogenation of olefins and aromatics in polymers with mean molecularweights from 40 000 to 120 000, wherein the support used has surfaceareas from 30 to 120 m²/g, 95% of the pore volume is formed by poreswith pore diameters of 30 to 100 nm and the proportion of the porevolume with pore diameters <20 nm is less than 4%. The hydrogenatingcomponent is Ni, Co, Rh, Ru, Pd, Pt or a combination thereof.

In U.S. Pat. No. 5,149,893, a Ni- or Co-calcium aluminate catalyst forthe hydrogenation of benzene is disclosed.

These catalyst systems are either preferred for the hydrogenation ofaromatics with low molecular weights or predominantly suitable for thehydrogenation of higher molecular weight aromatic compounds.

EP 1 331 033 discloses a process for the production of spherical metalsupport catalysts useful for the hydrogenation of aromatic substances.

DE 19909177 discloses supported nickel catalysts, preferably having ahigh zirconium content, for the hydrogenation of functional groups oforganic compounds.

The technical problem underlying the present invention is to provide acatalyst system with a high catalytic activity which is particularlysuitable for the hydrogenation of both higher and lower molecular weightaromatic compounds. Another object of the present invention is toprovide a process for the production of such catalysts and a method touse them.

The present invention solves the problem by the provision of a catalystfor the hydrogenation of unsaturated hydrocarbons, which catalyst is asupported nickel on silica (SiO₂) catalyst, has a nickel content of 40to 85 weight-% (calculated as NiO), a silicon content of 15 to 60weight-% (calculated as SiO₂), a titanium content of 0.5 to 5.0 weight-%(calculated as TiO₂), and does not contain more than 0.20 weight-% iron(calculated as Fe), wherein the catalyst has a monomodal Ni-crystallitesize distribution with a mean crystallite size of the reduced catalystof 1.5 to 3.5 nm, wherein the pore volume of pores with diameters from1.7 to 300 nm is at least 0.60 ml/g and wherein the proportion of thepore volume of pores with a pore diameter of 10 nm is at least 55%.

Thus, the present invention solves its technical problem in particularby the provision of a supported catalyst which in a preferred embodimenthas a nickel silicate phase, and which is characterised by a specificcombination of its composition, pore volume distribution and crystallitesize and distribution. Such a catalyst surprisingly provides, incontrast to conventional catalysts, a significantly higher activity andis of advantage due to its broad range of possible educts, in particularhigher and lower molecular weight aromatic compounds.

Weight-% values given in the present teaching refer, if not otherwisestated, to the weight of the dry total catalyst. In the context of thepresent invention, the components of the catalysts are to be selected inan overall amount not to exceed 100 weight-%.

The invention provides a nickel on silica hydrogenation catalyst whichis free of iron. In the context of the present invention, the term freeof iron refers to a catalyst which does not contain substantial amountsof iron, in particular, does not contain more than 0.20 weight-% Fe(calculated as Fe). In a more preferred embodiment, the iron content ofthe iron-free catalyst is at maximum 0.1, most preferably at maximum0.05 weight-% (calculated as Fe). In a particularly preferredembodiment, there is no detectable amount of iron in the catalyst,preferably no iron at all.

In a furthermore preferred embodiment, the sodium content of thecatalyst is low, preferably less than 1 weight-%, most preferably lessthan 0.5 weight-%, in particular less than 0.2 weight-% most preferablyless than 0.1 weight-% (calculated as Na₂O and relative to RO1).

The pore volume is determined according to BJH (Barrett, Joyner andHalenda). For the determination of pore volumes and proportions thereofpores with a diameter from 1.7 to 300 nm are considered, if nototherwise indicated.

In a particularly preferred embodiment, the nickel content is from 40 to80 weight-% (calculated as NiO on total catalyst weight).

In a furthermore preferred embodiment, the silicon content is from 15 to40 weight-% (calculated as SiO₂ on total catalyst weight).

In a preferred embodiment of the present invention, the reduction levelof the nickel in the present catalyst is expressed as ratio of metallicnickel to total nickel from 52 to 80%.

In a preferred embodiment of the present invention, the catalystcomprises, in particular, essentially consists, most preferred consistsof nickel, silica, titanium and one or more of the elements, preferablyin the form of its oxides, selected from the group consisting ofaluminium, magnesium, zinc, chromium and zirconium. In a preferredembodiment, the catalyst comprises, preferably essentially consists,particularly consists, in addition to nickel and SiO₂, of aluminium andtitanium, or their oxides.

In a most preferred embodiment of the present invention, the catalysthas an aluminium content of 2 to 10 weight-% (calculated as aluminiumoxide, Al₂O₂, on total catalyst weight).

In a preferred embodiment of the present invention, the catalyst has amagnesium content of 0.1 to 3.0 weight-% (calculated as magnesium oxide,MgO, on total catalyst weight).

In a preferred embodiment of the present invention, the catalyst has azinc content of 0.1 to 4.0 weight-% (calculated as zinc oxide, ZnO, ontotal catalyst weight).

In a preferred embodiment of the present invention, the catalyst has achromium content of 0.1 to 0.3 weight-% (calculated as chromium oxide,Cr₂O₂, on total catalyst weight).

In a preferred embodiment of the present invention, the catalyst has azirconium content of 0.1 to 3.0 weight-% (calculated as zirconiumdioxide, ZrO₂, on total catalyst weight).

The catalyst has in a preferred embodiment, a compacted bulk density ofat least 0.15, preferably at least 0.20, preferably at least 0.25kg/dm³, most preferably 0.25 to 0.35 kg/dm³.

In a furthermore preferred embodiment, the BET surface area is at least150, preferably at least 200, most preferably at least 250 m²/g. In afurthermore preferred embodiment, the nickel metal surface area is atleast 15, preferably at least 20, most preferably at least 23 m²/g.

In a particularly preferred embodiment, the silicate support containsadditionally one or more of the compounds selected from the groupconsisting of magnesium silicate, alumosilicate (Al₂O₃.SiO₂), TiO₂,nickel titanate, ZrO₂, nickel zirconate and ZnO. In a particularlypreferred embodiment, the catalyst comprises, preferably essentiallyconsists, particularly consists of 40 to 80 weight-% nickel (calculatedas NiO), 15 to 40 weight-% silicon (calculated on SiO₂), 2 to 10weight-% aluminium (calculated on Al₂O₃), 0.5 to 5.0 weight-% titanium(calculated as TiO₂) and 0.1 to 3.0 weight-% magnesium (calculated asMgO) and wherein the nickel of the catalyst has a reduction level of 52to 80%, wherein the catalyst has a monomodal crystallite sizedistribution with a mean crystallite size of 1.5 to 3.5 nm of thereduced catalyst and wherein the pore volume of the catalyst of poreswith a diameter from 1.7 to 300 nm is at least 0.60 ml/g and theproportion of the pores with a diameter of 10 nm is at least 55%.

Thus, the present invention solves its technical problem in particularby providing a nickel silicate phase based iron-free catalyst, whichcomprises, in particular essentially consists, particularly consists of(stated as element oxides) 40 to 85 weight-%, preferably 40 to 80weight-%, NiO, 15 to 60 weight-%, preferably 15 to 40 weight-%, SiO₂,and 0.5 to 5 weight-% TiO₂, wherein at least one of the componentsselected from the group consisting of 2 to 10 weight-% Al₂O₂, 0.1 to 3.0weight-% ZrO₂, 0.1 to 3.0 weight-% MgO, 0.1 to 4.0 weight-% ZnO and 0.1to 0.3 weight-% Cr₂O₃ is contained therein, wherein the nickel of thecatalyst has a reduction level of 52 to 80%, wherein the catalyst has amonomodal crystallite size distribution with a mean crystallite size of1.5 to 3.5 nm of the reduced catalyst and wherein the pore volume of thecatalyst of pores with a diameter from 1.7 to 300 nm is at least 0.60ml/g and the proportion of the pores with a diameter of ≧10 nm is atleast 55%. The present invention provides preferably such anickel-containing silica-supported catalyst as defined above, whereinthe silica support comprises one or more of the compounds selected fromthe group consisting of magnesium silicate, alumosilicate, TiO₂, nickeltitanate, ZrO₂, nickel zirconate and ZnO, preferably wherein the nickelis supported on nickel silicate and alumosilicate, with TiO₂.

The invention furthermore foresees that the catalyst is, in a preferredembodiment, a catalyst in form of a powder, in particular for use insuspension or slurry hydrogenation reactions. In a preferred embodimentof the present invention, the catalyst of the present invention is apowdered catalyst, whose pore volume is at least 0.68 ml/g. The particlesize of the catalyst in powder form lies, in a further preferredembodiment, in the range from 2 to 50 μm, preferably from 2 to 22 μm,both preferably with a d₅₀ value of 4 to 15 μm, preferably 4 to 10 μm.

In a furthermore preferred embodiment, the catalyst of the presentinvention is a formed or moulded catalyst, which is in the presentteaching also called a shaped catalyst, in particular for use in fixedor fluidised bed hydrogenation reactions. In a preferred embodiment, theshaped catalyst may be, for instance, in form of balls, spheres,tablets, pellets or extrudates.

In a preferred embodiment of the present invention, the catalyst is ashaped catalyst, wherein the proportion of the pore volume of pores witha pore diameter of 10 nm is at least 65%.

The present invention also provides a process for the preparation of anickel on silica catalyst as defined herein, wherein the catalystcomponents are co-precipitated.

The present invention also provides a process for the preparation of asupported nickel on silica catalyst, which process comprises reacting ametal salt solution which comprises a nickel ion source and a titaniumion source, with a sodium waterglass solution at a pH from 8.0 to 9.5 attemperatures from 70° C. to 100° C., preferably 85° C. to 100° C., so asto co-precipitate a catalyst material and recovering the co-precipitatedcatalyst material to obtain a supported nickel on silica catalyst.

Any reactant utilised in the process of the invention should besubstantially free of iron such that the resulting catalyst will notcontain more than 0.20 weight-% of iron (calculated as Fe).

In a particularly preferred embodiment, the above identified solutionsmay be added simultaneously to the precipitation vessel, or one afterthe other.

In the context of the present invention, waterglass is meant to be acompound which is a SiO₂ source. Thus, in particular, waterglass in thecontext of the present invention is, for instance, a water solublealkali silicate, SiO₂, mixtures of SiO₂ with alkali ions, alkali saltsor oxides, hydrogen silicates, silicates, for instance, sodium silicateor the like.

In the context of the present invention, a sodium waterglass solution istaken to mean a, preferably aqueous, solution containing a mixture ofwaterglass and sodium, the latter for instance in form of NaOH or Na₂CO₃(soda).

In a preferred embodiment of the present invention, the metal saltsolution comprises Ni²⁺ and TiO²⁺, and one or more of Al³⁺, Cr³⁺, Mg²⁺,Zn²⁺ and ZrO²⁺. In a preferred embodiment of the present invention, themetal salt solution is an acidic solution. In a preferred embodiment ofthe present invention, the metal salt solution is a nitrate solution.

In a preferred embodiment of the present invention, the sodiumwaterglass solution comprises one or more of Al(OH)_(r) ⁻, TiO₂, Zn andZrO₂. In a furthermore preferred embodiment of the present invention,the sodium waterglass solution is an alkaline solution.

In a preferred embodiment of the present invention, the pH value is keptconstant during the complete precipitation from 8.0 to 9.5. In apreferred embodiment of the present invention, the precipitation timeand the subsequent stirring time each is from 1 hour to 3 hours,preferably each from 1.5 to 2.5 hours, particularly each 2 hours. In aparticularly preferred embodiment, the precipitation is conducted understirring. In a particularly preferred embodiment, the pH value achievedat or after completion of the precipitation is ≧9.0, preferably is ≧9.1and is at maximum 9.5.

In a preferred embodiment, the invention provides a process as specifiedabove, wherein after the precipitation, the obtained catalystprecipitate is filtered. In a preferred embodiment, the filteredcatalyst precipitate, i.e. the filter cake obtained, is washed,preferably to a Na content of <0.2 weight-%, preferably <0.1 weight-%.

In a preferred embodiment of the present invention the, preferablywashed, filter cake is subsequently dried, for instance by flash drying,spray drying or simple drying in conventional drying devices.

For the production of catalysts in powder form it is preferred toprocess the filter cake via spray drying.

In a particularly preferred embodiment, the dried catalyst may befurther processed such as by granulation, preferably together withbinder components and/or water. In a preferred embodiment, thegranulated catalyst may be dried and calcined.

In a preferred embodiment of the present invention, the catalystobtained according to the above process, in particular the driedcatalyst, is calcined, for instance at temperatures from 120° C. to 350°C. In a furthermore preferred embodiment, the dried and calcinedcatalyst is reduced, preferably after a step of inerting the catalyst.

In a furthermore preferred embodiment, the dried catalyst is reduced,preferably in a fluidised bed, preferably in a stream of hydrogen,preferably at temperatures of 300° C. to 600° C., particularly 340° C.to 500° C. In another preferred embodiment, the reduction can, however,also be preformed in a rotary oven, a cylinder rotary kiln or anothersuitable installation. In a furthermore preferred embodiment, thereduced catalyst is stabilised, for instance, in a nitrogen/air,CO₂/nitrogen/O₂ or nitrogen/O₂ atmosphere.

The powdered catalyst may, in a particularly preferred embodiment of thepresent invention, be produced by spray or flash drying of the catalystprecipitate and subsequent processing, in particular calcination andreduction.

In a further preferred embodiment of the present invention, the presentcatalyst can be produced in powdered form by shaping of the driedprecipitation product, and subsequent reduction and stabilisation of thematerial with subsequent milling and screening of the reduced andstabilised catalyst.

The production of the shaped catalysts can be effected by known shapingprocesses. In accordance with the present invention, preferablyextrusion and drop formation have been found particularly advantageous.

The present invention also provides a catalyst obtained or obtainableaccording to the above identified preparation processes.

The present invention also provides a process for the hydrogenation ofunsaturated hydrocarbons, in particular aromatics, using the catalystsaccording to the present invention.

In a preferred embodiment of the present invention, the unsaturatedhydrocarbons are provided, contacted with at least one catalystaccording to the present teaching under suitable reaction conditions andhydrogenated hydrocarbons are obtained.

Temperatures and pressures suitable for conducting the present processfor the hydrogenation of unsaturated hydrocarbons can be determined bythe skilled person. In preferred embodiments, suitable reactiontemperatures are from 70° C. to 350° C., preferably 250° C. to 350° C.In a furthermore preferred embodiment, partial hydrogen pressures can beused, for instance, from 1 to 250 bar, preferably 1 to 150 bar,preferably 30 to 140 bar. The hydrogenation process of the presentinvention may be carried out in fixed bed reactors, fluid bed reactors,slurry reactors, loop reactors or the like.

Examples of aromatics which preferably may be hydrogenated according tothe present invention are kerosene, white oils, aromatic solvents orbenzene.

The advantages of the invention will be illustrated by means of thefollowing examples:

EXAMPLE 1 According to Invention

5 l of water are placed in a heatable precipitation vessel equipped witha stirrer and then titanium oxide is added in the form of an acidictitanyl sulphate solution. The solution is heated to a temperature of80° C. to 90° C. with stirring. On attainment of the temperature, theparallel addition of a metal nitrate solution and an aqueous precipitantsolution begins. In addition to nickel, the metal nitrate solutioncontains magnesium, aluminium and chromium. In addition to soda(Na₂CO₂), the precipitant solution contains a dissolved silicon dioxidecompound. During the precipitation, the pH value is kept constant at 8to 8.5. The precipitation time and further stirring time are each 2hours.

The mole ratio of nickel to SiO₂, Al₂O₃, Cr₂O₃, MgO and TiO₂ is1:0.5:0.04:0.0085:0.055:0.016.

After completion of the precipitation, the suspension is filtered andwashed with alkali-free water until the Na₂O content in the filter cakeis <0.2% based on the residue on ignition (RO1) of the filter cake heattreated at 800° C.

After the filtration and washing, the filter cake obtained is againredispersed in water and then sprayed in a commercial spray dryer. Thepowder material obtained has a grain size of 6 μm. Next, the product iscalcined for 2 hours at 350° C. and, after inerting, it is reduced in acurrent of hydrogen for 6 hours at 400° C. and stabilised in aCO₂/nitrogen stream with an oxygen content of 0.1 to 1 vol. % attemperatures below 80° C.

The reduced and stabilised catalyst contains approx. 55% nickel based onthe total catalyst. It has a nickel reduction level, expressed by theratio of metallic nickel to total nickel, of approx. 70%. The catalystshowed a monomodal Ni-crystallite size distribution. The mean nickelprimary particle size (i.e. the mean crystallite size of the reducedcatalyst) of the catalyst further reduced at 180° C. is about 3 nm. TheXRD spectrum confirms the presence of a nickel silicate phase. The porevolume is 0.73 ml/g. The pore volume with pore diameters 10 nm is 0.42ml/g.

EXAMPLE 2 According to Invention

15 l of water are placed in a heatable precipitation vessel and thenkieselguhr as the SiO₂ component and solid TiO₂ (P 25, Degussa Co.) areadded with stirring. This is followed by the addition of an aqueoussodium hydroxide solution (10%). After heating of the solution to 85°C., the metered addition of a combined metal nitrate solution, whichcontains nickel, aluminium, magnesium and chromium ions, begins. Themole ratio of nickel to SiO₂, Al₂O₃, MgO, TiO₂, Cr₂O₃ and ZnO is1:0.4:0.038:0.05:0.016:0.004:0.006.

The precipitation time and subsequent stirring time at a meantemperature of 85° C. is approx. 2 hours for each. After theprecipitation and subsequent stirring, the pH value is about 8.5. Afterthe filtration and washing, the filter cake obtained is againredispersed and then sprayed in a commercial dryer. The powder materialobtained has a mean grain size of 9 μm. The dry product is calcined at350° C. in a stream of inert gas and then reduced in a stream ofhydrogen in a fluidised bed at 350° C. for 2 hours. After the reduction,it is cooled in a stream of nitrogen, and stabilised in anitrogen/air/CO₂ mixture with O₂ contents of 0.1-1 vol. %.

The reduced and stabilised catalyst contains approx. 58% nickel based onthe total catalyst. It has a nickel reduction level, expressed by theratio of metallic nickel to the total nickel, of approx. 55%. Thecatalyst showed a monomodal Ni-crystallite size distribution. The meannickel primary particle size (i.e. the mean crystallite size of thereduced catalyst) of the catalyst further reduced at 180° C. is 2.7 nm.The XRD spectrum confirms the presence of a nickel silicate phase. Thepore volume is 0.71 ml/g. The pore volume with pore diameters ≧10 nm is0.40 ml/g.

EXAMPLE 3 According to Invention

10 l of water are placed in a heatable precipitation vessel and then theaddition of a sodium aluminate solution (40 g Al₂O₃/1 solution, 100 gNaOH/1) and waterglass solution (50 g SiO₂/1 solution) is effected withstirring. After heating of the solution to 90° C. to 95° C., the meteredaddition of an aqueous nickel-, magnesium- and zirconium nitratesolution up to a pH value of 8.5 is started. The metal nitrate solutionadditionally contains TiO₂ in form of a titanyl sulphate solution. Afterattainment of the pH value of about 8.5, the parallel addition of theremaining nickel nitrate solution and an aqueous NaOH solution (10%) attemperatures of 90° C. to 95° C. begins. The precipitation time is 1hour, the subsequent stirring time approx. 2 hours.

The mole ratio of nickel to SiO₂, Al₂O₃, MgO, TiO₂ and ZrO₂ is1:0.39:0.038:0.036:0.016:0.01.

The further processing of the catalyst takes places as described inExample 1. The reduction is performed at a temperature of 420° C.

The reduced and stabilised catalyst contains approx. 60% nickel based onthe total catalyst. It has a nickel reduction level of approx. 80%. Thecatalyst showed a monomodal Ni-crystallite size distribution. The meannickel primary particle size (i.e. the mean crystallite size of thereduced catalyst) of the catalyst further reduced at 180° C. is 2.8 nm.The XRD spectrum confirms the presence of a nickel silicate phase. Thepore volume is 0.77 ml/g. The pore volume with pore diameters 10 nm is0.51 ml/g.

EXAMPLE 4 According to Invention

5 l of water and solid TiO₂ (P 25, Degussa Co.) are placed in a heatableprecipitation vessel, then the suspension is heated with stirring to atemperature of 90° C. to 95° C. After attainment of the temperature, theparallel addition of a combined metal nitrate solution, which containsnickel, aluminium and magnesium in the form of the nitrates and analkaline solution which is an aqueous solution of the precipitant sodaand a dissolved SiO₂ compound, takes place. During the precipitation,the pH value is constantly adjusted to 8.0 to 8.3. The precipitation andsubsequent stirring time are each approx. 2 hours.

The mole ratio of nickel to SiO₂, Al₂O₃, MgO and TiO₂ is1:0.328:0.037:0.053:0.032.

After completion of the precipitation, the precipitation suspension isfiltered and the filter cake washed with pure condensate until the Na₂Ocontent is <0.05% based on the filter cake weight taken. Next, thefilter cake is dried at temperatures from 120° C. to 140° C. down to aresidue on ignition (800° C.) of at least 70% and then calcined at 350°C. to 380° C. After completion of the calcination, the residue onignition of the calcined material is at least 90%. The product obtainedis now reduced in a suitable unit in a stream of hydrogen attemperatures from 420° C. to 430° C. for 10 hours and then stabilised atambient temperature in an O₂ containing stream of nitrogen.

The reduced and stabilised catalyst is then finely ground in an inertgas mill under a protective atmosphere.

The finished powder catalyst has a nickel content of 60%, the reductionlevel is approx. 80%, and the mean crystallite size (i.e. the meancrystallite size of the reduced catalyst) of the catalyst furtherreduced at 180° C. is 3.1 nm. The catalyst showed a monomodalNi-crystallite size distribution. The mean particle size of the catalystis 15 μm, and the total pore volume is 0.70 ml/g, and the pore volumewith pore diameters of ≧10 nm is 0.39 ml/g.

EXAMPLE 5 According to Invention

8 l of water and titanyl sulphate are placed in a precipitation vessel.After this, the addition of a sodium waterglass solution takes placewith stirring within 30 mins. During the addition, the heating to thedesired precipitation temperature of 90° C. takes place. Afterattainment of the temperature, a pH value of approx. 8 is attained byaddition of a combined nickel-, magnesium- and aluminium nitratesolution, and the mixture is then stirred for a further 30 mins. Afterthis, the precipitation process is continued in that in parallel asodium hydroxide solution (150 g/l) and the remaining metal nitratesolution are metered in. During the precipitation, the temperatureremains constant at 90° C. The precipitation time and subsequentstirring time are each about 1 hour. The mole ratio of nickel to SiO₂,Al₂O₃, MgO and TiO₂ is 1:0.65:0.038:0.05:0.016.

The precipitation suspension is then filtered and the filter cake washedwith very clean condensate. After this, the filter cake is againdispersed in water and made into drop form by the alginate method. Afterdrying and calcination at temperatures of 130° C. and 400° C.respectively, the reduction of the moulded bodies is effected at atemperature of 420° C. in a stream of hydrogen. The stabilisation isperformed as described in Example 1.

The finished catalyst has a nickel content of approx. 52%, the reductionlevel is approx. 70%, the mean crystallite size (i.e. the meancrystallite size of the reduced catalyst) of the catalyst furtherreduced at 180° C. is 3.2 nm and the catalyst has a particle size of 2-3mm. The catalyst showed a monomodal Ni-crystallite size distribution.The pore volume is 0.70 ml/g, and the pore volume with pore diameters of10 nm is 0.49 ml/g.

EXAMPLE 6 Comparative Example

10 l of water were placed in a precipitation vessel and then heated to80° C. with stirring. After this, the parallel addition of a combinedmetal nitrate solution containing 1.4 kg nickel, 0.050 kg MgO, 0.050 kgAl₂O₃ and 0.0056 kg Fe and a soda/waterglass solution, which contains2.9 kg soda and 0.345 kg SiO₂ was effected with stirring at a constanttemperature of 80° C. The pH value during the precipitation was 7.5. Theprecipitation process was completed after 1 hour. After completion ofthe precipitation, the suspension was filtered and washed. The filtercake obtained was then dried at 110° C., finely ground and calcined at350° C. The reduction of the catalyst educt material was effected in thefluid phase at a temperature of 400° C. After the stabilisation of thecatalyst in a nitrogen/air mixture, the finished catalyst had thefollowing composition:

60% nickel, 18% SiO₂, 2.7% Al₂O₃, 2% MgO and 0.3% Fe₂O₃.

The nickel reduction level in the catalyst was about 65%, and the nickelprimary particle size about 3.5 nm. The pore volume (for pores with adiameter of 2 to 60 nm) is 0.35 ml/g. The pore volume is 0.41 ml/g, andthe pore volume with pore diameters of 10 nm is 0.17 ml/g.

EXAMPLE 7 Comparative Example

10 l of water and the soda/waterglass solution used in Example 6 andbeing of the same composition were placed in the vessel and then heatedto 80° C. After this, the addition of the combined metal nitratesolution, which contained 1.4 kg nickel, 0.050 kg Al₂O₃ and 0.0056 kg Fewas effected with stirring and a constant temperature of 80° C. After aprecipitation time of 1 hour, the pH value of the precipitationsuspension was 7.3. The precipitation slurry was filtered, washed andthen sprayed in a commercial spray dryer. The mean particle size of thesprayed granules was approx. 10 μm. The calcination, reduction andstabilisation were effected in the fluidphase.

The finished catalyst had the following composition: 62% nickel, 19%SiO₂, 3% Al₂O₃ and 0.35% Fe₂O₃.

The nickel reduction level in the catalyst was 70%, and the nickelprimary particle size 3.8 nm. The pore volume (for pores with a diameterof 2-60 nm) is 0.34 ml/g. The pore volume is 0.39 ml/g. The pore volumeof the pores with pore diameters ≧10 nm is 0.13 ml/g.

EXAMPLE 8 Comparative Example

A dried and ground Ni/SiO₂ starting material with mean particle size of10 μm and a bulk density of 0.7 kg/l was mixed with tylose as binder andthen dispersed in a laboratory kneader with the addition of condensatewater, nitric acid and silica sol solution. Based on the solids contentof this kneader batch, the addition of tylose amounts to 2.5%. After akneading time of 15 mins, the complete batch was shaped into 3 mmcylindric extrudates in a laboratory extruder with a cutting device. Themoist extrudates obtained were further processed into spheres in alaboratory spheroniser (Caleva Co., Model 120, England). Thesphere-shaped material obtained was then dried at 130° C.

The starting material was reduced at 400° C. in a stream of hydrogen asalready described and stabilised under standard conditions.

The finished catalyst contains approx. 55% nickel and has a reductiondegree of approx. 75%. The mean nickel crystallite size is 4.5 nm. Thecatalyst shows a broad particle size distribution with diameters of 2-4mm. The pore volume is 0.30 ml/g, and the proportion of pores with porediameters >10 nm is only 0.02 ml/g.

EXAMPLE 9 Comparative Catalysis

Table 1 below shows the composition of catalysts according to theinvention and comparative catalyst used in the following comparativeanalysis

TABLE 1 wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% wt.-% ExampleNiO SiO2 Al2O3 TiO2 ZrO2 MgO Cr2O3 ZnO Fe2O3 1 70 25 2 1 2 0.2 2 73 21.82.05 0.9 1.9 0.15 0.2 3 75 20.8 2 1 0.4 1.2 4 73 18.5 4 2.3 2.2 5 6529.5 2.1 1.2 2.2 6 78 16 3.2 2.3 0.5 7 79 16.9 3.5 0.6 8 72 28 9 70 2010

For the catalytic assessment, a commercial sphere-shaped nickelalumosilicate catalyst 9 with the following physico-chemicalcharacteristics was also used:

TABLE 2 Nickel content (wt. %) 55 Nickel reduction level (%) 60 Bulkdensity (kg/l) 0.95 Mean particle diameter (mm) 2.5 Particle diameterrange (mm) 1.6-4.7 Pore volume (ml/g) 0.27 Pore volume >10 nm 0.19Nickel crystallite size (nm) 5.1

Catalyst 5 produced according to the invention and the comparativecatalysts 8 and 9 were used for the catalytic assessment of thehydrogenation of aromatics in a fixed bed process.

For the catalytic characterisation of the Ni supported catalysts, thearomatics hydrogenation of kerosene using an integral flow reactor(internal diameter: 25 mm) was used. The incorporated catalyst volumewas 50 ml. The 50 ml of catalyst were in each case incorporated in 10portions with 10 portions of SiC in a volume ratio of 1:1. Before thecatalytic reaction, the catalysts were reactivated in a stream ofhydrogen (50 l/hr) over a period of 4 hours at 250° C. As feed, akerosene with an aromatics content of 18 weight-% and a sulphur contentof 1.1 ppm was used. The other experimental conditions were:

Reaction pressure: 30 bar Reaction temperature: 85° C., reaction time:40 hours 100° C., reaction time: 80 hours LHSV: 1.3 Gas - product ratio:400 l H₂/l kerosene

The results are shown in Table 3.

TABLE 3 Reaction temperature: Reaction temperature: Catalyst 85° C. ppmaromatics 100° C. ppm aromatics Example 5 1490 139 according toinvention comparative 2640 259 example 8 comparative 3105 298 example 9

A comparison of the catalytic measurement results shows the superiorityof the catalysts according to the invention: the degree of hydrogenationor degradation of the aromatics up to the ppm range is significantlygreater with the catalyst according to the invention than with theconventional catalysts.

The catalytic characterisation of the powder catalysts was carried outusing a stirred autoclave from the Autoclave Engineers Co.: 210 g of aresin (mean molecular weight: 2750 g), 90 g of Shellsol and 1.8 g ofcatalyst were transferred into the autoclave and after inerting theautoclave was charged with hydrogen to a pressure of 4 bar. Next, theautoclave content was heated to a temperature of 270° C. Afterattainment of this temperature, the reaction pressure of 90 bar wasestablished and the stirrer then set into operation. The stirring speedwas 2200 rates per minute. The hydrogen consumption under constantpressure as a function of the reaction time was measured. The mean ratein 1H₂/hr g_(catalyst) calculated from the hydrogen consumption betweenthe 10th and 30th minute after the start of reaction served as themeasure of activity.

The results of the catalytic measurement results are shown in Table 4.

TABLE 4 Hydrogenation activity Catalyst in l H₂/hr g Example 1 accordingto invention 15.6 Example 2 according to invention 16.1 Example 3according to invention 15.2 Example 4 according to invention 16.0Example 6 (comparative example) 12.8 Example 7 (comparative example)13.3

The data in Table 4 clearly shows that the catalysts according to theinvention have a higher hydrogenation activity than the comparativecatalysts.

What is claimed is:
 1. A catalyst for the hydrogenation of unsaturatedhydrocarbons, which catalyst is a supported nickel on silica catalyst,has a nickel content of 40 to 85 weight-% (calculated as NiO), a siliconcontent of 15 to 60 weight-% (calculated as SiO₂), a titanium content of0.5 to 5.0 weight-% (calculated as TiO₂), and does not contain more than0.20 weight-% iron (calculated as Fe), wherein the catalyst has amonomodal Ni-crystallite size distribution with a mean crystallite sizeof the reduced catalyst of 1.5 to 3.5 nm, a pore volume of at least 0.60ml/g and wherein the proportion of the pore volume of pores with a porediameter of ≧10 nm is at least 55%.
 2. A catalyst as claimed in claim 1,wherein the reduction level of nickel in the catalyst is from 52 to 80%.3. A catalyst as claimed in claim 1, which has an aluminum content of 2to 10 weight-% (calculated as Al₂O₃).
 4. A catalyst as claimed in claim1, which has a magnesium content of 0.1 to 3.0 weight-% (calculated asMgO).
 5. A catalyst as claimed in claim 1, which has a zinc content of0.1 to 4.0 weight-% (calculated as ZnO).
 6. A catalyst as claimed inclaim 1, which has a chromium content of 0.1 to 0.3 weight-% (calculatedas Cr₂O₃).
 7. A catalyst as claimed in claim 1, which has a zirconiumcontent of 0.1 to 3.0 weight-% (calculated as ZrO₂).
 8. A catalyst asclaimed in claim 1, which is a powdered catalyst whose pore volume is atleast 0.68 ml/g, or which is a shaped catalyst wherein the proportion ofthe pore volume of pores with a pore diameter ≧10 nm is at least 65%. 9.A catalyst as claimed in claim 1, wherein the support contains one ormore of the compounds selected from the group consisting of magnesiumsilicate, aluminosilicate, TiO₂, nickel titanate, zirconium dioxide,nickel zirconate and ZnO.